As nouns the difference between darl and darr

As nouns the difference between darl and marl

is that darl is (informal) darling while marl is a mixed earthy substance, consisting of carbonate of lime, clay, and possibly sand, in very variable proportions, and accordingly designated as calcareous, clayey, or sandy.

As a verb marl is

to cover, as part of a rope, with marline, marking a peculiar hitch at each turn to prevent unwinding.